Methods and articles of the invention relate to security paper, i.e. paper which is ideally resistive to counterfeiting or other attempts at fraudulent imitation and which is suitable for use in the production of security documents.
xe2x80x9cSecurity paperxe2x80x9d or xe2x80x9csecurity documentxe2x80x9d generally means any paper or document having a value such as to render it vulnerable to counterfeiting attempts. Typical examples of such papers or documents are papers for use in passports; banknotes; bank checks; traveler""s checks; money orders; bankers drafts; bearer bonds; share certificates and other certificates; stamps; postal orders; identity documents; registration documents, driving licences, vehicle road tax licences and other licences or permits; electoral papers; savings or bank account passbooks; lottery tickets; admission tickets; travel tickets; vouchers; coupons; tokens; and shipping and other transport documents; as well as other documents and papers.
Papers for use in labels or distinctive packaging may also be subject to counterfeiting, particularly if they bear a manufacturer""s name and/or a brand name. Considerable publicity has been given in recent years to the problems of illegal marketing of cheap copies of branded goods. The copies are liable to be packaged and branded in much the same way as genuine goods from an original or authorised manufacturer. Thus the use of security paper in the labels and/or packaging of the goods provides a means of verifying the authenticity of branded goods. Verifiable label or packaging paper is therefore also within the scope of the term xe2x80x9csecurity paperxe2x80x9d as used in this specification.
Further, high security documents, such as passports and banknotes, often carry a palpably-detectable surface profile pattern or design which is imparted to selected areas of the finished paper at the printing stage. The palpable, or tactile, effect can generally be produced by embossing. The palpable pattern enables the document to be partially authenticated by touch, in that a document with no such selective palpable pattern is immediately revealed as counterfeit.
Conventional dry embossed patterns suffer from the drawbacks that they increase production costs at the printing stage, and that they can wear away in use. The intricacy of the pattern applied, and thus the level of security obtainable, is also limited when the pattern is produced by embossing previously formed and dried paper. Additionally, security papers often contain two-sided or backside colorants for bank sorting purposes as well as a line pattern printed on the sheet to deter xe2x80x9ccut-and-pastexe2x80x9d fraud. Traditionally, these colorant and line pattern features require the paper to be coated and/or printed off line, and thus produce an effect that is easily reproduced by skilled criminals.
It is thus an object of this invention to put some property in the paper which is difficult to copy or otherwise make on small scale, and which will not be reproduced in known copy machines and/or duplicating machines.
It is another object of this invention to teach a security paper wherein transmission of light through one portion of the security paper is discernibly different from transmission of light through another different portion of the security paper, when viewed with a human eye.
It is yet another object of this invention to teach a security paper having substantially the same fiber density throughout the paper.
It is still another object of this invention to teach a security paper which demonstrates reflected light attenuation at at least a first portion of the paper being greater than reflected light attenuation at a second different portion of the paper, so as to appear to leave a darker reflected image at the first portion of the paper than at the second portion.
In a first family of embodiments, the invention comprehends a security paper comprising a light-colored base paper having a non-protection area of a first thickness, and a protection area of a second thickness on at least one major surface of the base paper wherein the first thickness is greater than the second thickness. The base paper comprises colorant whereby the protection area exhibits a translucence when viewed using transmitted light, and exhibits the colorant as a darker color indication, relative to the non-protection area, when viewed using reflected light.
In preferred embodiments, the thickness of the protection area is preferably sufficiently thin that sufficient transmitted light can pass therethrough to establish color intensity difference between the non-protection area and the protection area.
In preferred embodiments, the thickness of the protection area is sufficiently thin, and fibers of the protection area are sufficiently dispersed, that at least some transmitted light can pass therethrough.
In some embodiments, the colorant is applied to only one major surface of the base paper.
In preferred embodiments, the colorant is disposed on or close to a major surface of the base paper, and selectively congregated in depressions of the protection area, the depressions being defined by the differences in thickness between the non-protection area and the protection area, thus to concentrate the colorant at the protection area.
Transmission of light through a combination of paper fibers and the colorant, both being disposed at the protection area, is discernibly different from transmission of light through the non-protection areas of the base paper, when viewed with a human eye.
Generally, the non-protection area has substantially the same fiber density as the protection area.
In preferred embodiments, quantity and opacity of the colorant at the protection area is sufficiently intense that reflected light attenuation at the protection area is greater than reflected light attenuation at the non-protection area, so as to appear to leave a darker reflected image at the protection area than at the non-protection area.
The second thickness of the protection area is preferably established while solids-content of a precursor web mass of fibers of the base paper is 10% by weight or less, thus enabling lateral movement of fibers and sustaining substantially uniform distribution of fiber density at and adjacent the protection area during establishment of the protection area.
Preferably, the colorant is applied to the base paper when such base paper is substantially dry.
Generally, the colorant comprises at least one of pigments, dyes, and chromogenic materials, such colorants developing color indications under controlled conditions, such as pH, moisture, impact, crushing, and the like.
In some embodiments, the protection area can have the form of at least one of letters, numbers, and symbols.
In some embodiments, the base paper comprises a protection area on both major surfaces thereof.
In a second family of embodiments, the invention comprehends a method of manufacturing security paper. The method includes forming a light-colored base paper having a non-protection area of a first thickness, and a protection area of a second thickness on at least one major surface of the base paper wherein the first thickness is greater than the second thickness. The method also includes treating a major surface of the base paper with a colorant whereby the protection area thus exhibits a translucence when viewed using transmitted light, and exhibits the colorant as a darker color indication, relative to the non-protection area, when viewed using reflected light.
In a third family of embodiments, the invention comprehends a method of manufacturing security paper of varying thickness. The method includes, at a wet end of a papermaking machine, affecting a web mass of base paper fibers, moving in a machine direction, with a patterned roll, while solids-content of the web mass is still 10% by weight or less, thus creating protection areas as depressions in the resultant security paper reflecting the pattern of the roll. The method also includes, after positioning of the paper fibers in the web mass has been substantially established, adding a limited quantity of colorant to at least one side of the base paper such that the colorant congregates selectively in the depressions of the protection areas.
In preferred embodiments, the patterned roll has a rotational velocity different from velocity of the web mass of base paper fibers in the machine direction.
The pattern of the patterned roll preferably comprises an axial peripheral protrusion which is designed and configured to move the paper fibers laterally, thus maintaining the uniform density of such security paper at and adjacent the protection areas.
In some embodiments, the method includes adding the colorant to at least one side of the base paper at a uniform application rate across the protection areas and a non-protection area, wherein the colorant congregates selectively in the depressions of the protection areas due to a pooling effect, thus developing sufficient opacity in the depressions that reflected light attenuation at the protection areas is greater than reflected light attenuation at the non-protection area, so as to exhibit a darker reflected image at the protection areas than at the non-protection area.
In other embodiments, the method includes applying the colorant to at least one side of the base paper, wherein the protection areas exhibit a translucence when viewed using transmitted light, and exhibit the colorant as a darker color indication, relative to non-protection areas, when viewed using reflected light.